The present invention relates generally to the field of security devices and more specifically to alarm systems which frighten burglars and intruders.
In our crime ridden society, many people have found it advantageous to keep a dog in order to scare away intruders. Ordinarily, a dog will bark loudly when someone rings the doorbell or knocks on the door. Most burglars want to be certain that no one is at home before attempting a burglary and will often test for this by knocking, ringing the doorbell, and then checking the front door to see if the door has been left unlocked. The response of a loud dog's bark to any of these is likely to dissuade the would-be burglar.
The keeping of dogs has certain inherent shortcomings. Not the least of these is that some people simply do not like dogs. Additionally, they tend to be expensive to keep, unsanitary, noisome and, occasionally, dangerous even to the owner.
A number of solutions to this dilemma have been proposed. L. Markham (U.S. Pat. No. 4,023,151) provides a communication appliance device which emits an audible message to anyone who breaks a beam of light or steps upon a pressure operated switch. While this might be used as an alarm, it may be easily circumvented by not stepping on the pressure switch or stepping over the light beam. Also, any sound emitted by the door mounted loudspeaker would not be likely to intimidate a burglar.
R. Reyes (U.S. Pat. No. 4,212,007) provides a combined burglar frightening device and alarm which proposally frightens a burglar by sounding a "woof-woof" sound while causing a model of a snarling dog's torso to move back and forth ominously. However, as common experience indicates, a dog sensing an intruder is not likely to remain in place and bob back and forth.
G. O'Connell (U.S. Pat. No. 3,938,120) provides a talking door sentinel which is mounted to the top of a door and emits a potentially threatening sound from a self contained speaker. Firstly, a burglar would have to succeed in opening the door before this alarm could even begin to sound. Also, the source of the sound would become instantly clear to even an inexperienced thief.